Although exposure to asbestos has been definitely associated with the development of lung cancer, the magnitude of the risk has not been defined in persons who are exposed to relatively minute doses of asbestos. Even small amounts of asbestos together with cigarette smoking, have been shown to have a synergistic effect in producing lung cancer. In a preliminary study of post mortem lungs, using techniques to extract and concentrate bodies, we found large numbers of asbestos bodies more frequently in our lung cancer patients than in a control population without lung cancer. This difference occurs in cases where asbestos bodies are easily overlooked on routine histologic sections. We now propose to confirm this finding by quantifying the number of asbestos bodies in the lung of more patients with lung cancer in a population with low asbestos exposure. Lungs from control patients matched for age, sex and smoking history will be used for comparison. Specific identification of fibers as asbestos will be carried out by ultrastructural morphology and electron diffraction. It is hoped that quantitative criteria of "significant" exposure to asbestos can be determined, and the magnitude of the problem of increasing prevalence of asbestos in the environment clarified. BIBLIOGRAPHIC REFERENCE: Martha L. Warnock and Andrew M. Churg: Association of Asbestos and Bronchogenic Carcinoma in a Population with Low Asbestos Exposure. Cancer 35: 1236-1242, 1975.